Gen 2 definitely. I loved Gen 1 to death, and as such I played it to death, so when Gen 2 came out it was like a huge breath of fresh air the likes of which I've never before felt. Playing it the first time, it felt quirkier and more special than Gen 1, and it was just such a great feeling to be able to begin again somewhere I didn't know and discover all new secrets. That was the first time that happened to me, since my first playthrough of Gen 1 I was kinda busy figuring out how to Pokemon